According to The Independent, the drawing was first used in 1899 by Joseph Jastrow, a psychologist who wanted to demonstrate that perception is not just about sight but also a mental activity. His research found that those who were able to see both animals easily could name five unusual uses for an everyday item, whereas those who could only see one animal or struggled to switch between the two animals could only come up with two unusual uses for an everyday item.

The results of Jastrow’s research suggest that those who are able to see both animals in the drawing easily and switch between the two may be more creative.

What you see can also be influenced by other factors, such as time of year, according to The Independent. During the Easter season, more people see a rabbit. In the fall, more people see a duck.